This invention lies in the field of high-precision electronic components, and relates to the preparation and handling of the liquid chemicals used in the manufacture of such components at various stages of the manufacturing process.
A major concern at every stage in the manufacture of electronic components is contamination. Control of contamination is critical to product quality, and an extremely high level of cleanliness and purity in the manufacturing environment is needed for obtaining acceptable product yield and maintaining profitability. These requirements are particularly acute in the manufacture of very high density circuitry as well as in ultra-precision bearings, recording heads and LCD displays.
Sources of contamination include the manufacturing facility, personnel and processing equipment. In many cases, contamination can be lowered to acceptable levels by the use of xe2x80x9cclean roomxe2x80x9d techniques such as isolation, air filtration, special equipment and special clothing and body coverings to avoid contact between the operator and the manufacturing materials. With ultra-high precision manufacturing, the highest levels at which defects can be tolerated are particularly low and control over sources of contamination is even more critical.
A problematic source of contamination in ultra-high precision manufacturing is the liquid chemicals used in the manufacturing process. Cleaning and etching agents and other treatment chemicals must be extremely pure and free of particulate matter to produce acceptable product in high yield. Chemicals brought in from outside sources, however, contain inherent contamination which they bring to the manufacturing area. Contamination is contributed by the preparation of the chemicals, the packaging in which the chemicals are shipped as well as the packaging operation, the handling the chemicals receive during transfer from the manufacturer, and decay of the chemicals in the packaging during shipment or storage.
Further difficulties arise in those procedures which require treatment chemicals which do not meet Department of Transportation regulations, and therefore cannot be shipped in a manner which requires conformance with these regulations. Examples are nitric acid at concentrations exceeding 70%, high-purity oleum, ammonium hydroxide at concentrations exceeding 28%, and hydrogen peroxide without stabilizers.
Clearly there is a need for a reliable means of supplying these treatment chemicals at a purity level which will produce a high yield of acceptable product in ultra-high precision components, and which can meet the requirements of advancing electronics technology.
A system for supplying liquid chemicals of ultra-high purity to a production line for high-precision electronic devices has now been developed. The treatment chemicals are prepared at the site of use in a production facility, providing a high level of control over the manufacturing process and the purity and composition of the treatment chemicals, which in turn allows the manufacture of extremely high density semiconductors with a high yield of acceptable products. According to this invention, the liquid treatment chemicals are prepared at the point of and immediately prior to their use, from gaseous starting materials which have been purified to a level compatible with semiconductor manufacturing standards. The chemicals are prepared directly at the concentrations and dilutions in which they will be used in the treatments, without the need for packaging or transport, or the need for mixing these chemicals with diluents, solvents or other chemicals which are potential sources of contamination.
Preparation of a treatment chemical in accordance with this invention consists of reacting a purified gaseous starting material with other materials, gaseous or liquid, which have been similarly purified to achieve the desired liquid product. This may involve contacting the gaseous starting material with a mist or stream of highly purified water or other liquid to form a liquid solution, or reacting the gaseous starting material with other highly purified gaseous or liquid materials to produce a product which is itself liquid or immediately dissolved in a liquid solvent. The resulting high-purity treatment liquid is then passed directly to a workstation on the production line, where the treatment liquid contacts the surface of the workpiece to serve its intended function with no intervening exposure to potential sources of contamination such as storage and shipping containers and less than ultra-clean environments.
This invention is applicable to processing and cleaning liquids in general, with particular applicability to cleaning solutions, developing solutions, etching solutions and stripping solutions, and permits treatment of the workpiece in a manner which is free of contamination, to result in a product free of defects. In this manner, semiconductors with extremely detailed, concentrated and accurate circuitry, bearings, glasses and other materials whose performance relies on high precision can be prepared in high yield.